1. Field of Invention
Invention relates to the measurement of dimensions in gratings and more particularly to the generation and use of configurable libraries of grating profiles.
2. Description of Related Art
Features on semiconductor devices and transmitters of optical fiber links are being formed that are less than one micron in width. Measurement of these sub-micron features is increasingly difficult as the size of the features become smaller. However, knowledge of the dimensions of gratings or periodic structures is essential in order to determine if the dimensions of the features are within the acceptable ranges and if a particular fabrication process causes the sidewalls of the features to be tapered, vertical, T-topped or undercut.
Traditionally, a sample was cleaved and examined with a scanning electron microscope or similar device. This method is slow, expensive, and only provides one measurement number seen from the top of the feature. Angular scatterometry have been employed to measure linewidths of gratings but the process requires a setup of multiple detectors at different angles from the incident beam to measure the diffraction of the scattered light. Again, this is difficult to implement because of the setup required.
Spectroscopic reflectometry and ellipsometry are used to beam light on the grating and measure the spectra of reflected signals. Current practices basically use an empirical approach where the spectra of reflected light is measured for a known width of features in a grating. This process is time consuming and expensive even for a limited library of profiles of grating dimensions and the associated spectrum data of reflected light. There is a need for a less laborious and less expensive method of creating the library of profiles and associated spectrum data.
Furthermore, if such a library were built for a wide range of profiles, it would be very useful to have access and use of the library in a real-time environment. An extensive library of profiles and spectrum data would however be inefficient for searching purposes needed for real-time work. For a short fabrication run, a client may only need a small subset of the extensive master library. Thus, there is a need for a method and system of providing libraries of grating profiles that are responsive to both long term and short term requirements of the client.
Invention resides in a method and a system for creating configurable libraries of grating profiles and spectrum data. The method comprises specifying a parameter set of a plurality of dimensions of a grating and compiling a master library of grating profiles corresponding to the combinations of the parameter set of the plurality of dimensions at different resolutions and the calculated spectrum data.
One embodiment is a system for creating a run-time library of profiles comprising a master library of profiles and the calculated spectrum data; a storage medium for storing the run-time library; a computer coupled to the master library and the storage medium; and a run-time compiler operable in the computer, for generating the run-time library; wherein the computer activates the run-time compiler to prompt for identification of the selection parameter set, to validate the selection parameter set, to extract the profiles from the master library, and to create a run-time library.
Furthermore, the present invention includes a method for evaluating grating spectrum data, the method comprising comparing a grating spectrum data to the ranges of grating calculated spectrum data in a run-time library; flagging the grating spectrum data as falling within the profile calculated spectrum data ranges in the run-time library or flagging the grating spectrum data falling outside the profile calculated spectrum data ranges in the run-time library; selecting the profile instance in the run-time library whose calculated spectrum data is closest to the grating spectrum data; and recording the selected profile instance.
Another embodiment of the present invention is a system that invokes a compiler when a set of conditions is met. The system comprises a master library; a starting run-time library compiled with a starting set of trigger conditions; a replacement run-time library, for replacing the starting run-time library; a run-time compiler; a computer; and a comparator operable in the computer, for comparing the calculated set of process trigger values to the starting set of trigger conditions; wherein the comparator, detecting a condition where the calculated process trigger values meet the requirements of the starting set of trigger conditions, automatically invokes the run-time compiler to compile the replacement run-time library.
The present invention also includes a method of providing a service for generating a library of grating profiles, the method comprising contracting by a client and a vendor, where in return for remuneration from the client, the vendor provides access to the systems, processes, and procedures to generate the library or generates and delivers the library.